Google Play Store ignores background data restrictions

I’ve been hit with data overages in the past so I lock down background data usage on several apps. This includes the Play Store. I’ve also disabled auto-update within that app.

However, at around 5:45PM I’m hit with the Play Store downloading about 20 MB of data. I’m told that disabling auto-update doesn’t apply to the Play Store itself. What gives?

I’m using a Nexus 5X with Oreo 8.1.0.